The present invention relates generally to the field of medical catheters, and in particular, to ultrasonic imaging medical catheters.
In recent years, the use of ultrasound systems for medical diagnostics has continued to grow. Ultrasonic systems are used in a plethora of medical fields and in a wide-ranging number of diagnostic areas. As the desire to use ultrasonic imaging systems has grown, so has the level of sophistication of those systems.
To assist physicians and staff in performing diagnostic and therapeutic procedures, a number of ultrasonic imaging systems have been designed for use with catheters. In general, these systems comprise a single transducer element, frequently made of piezoelectric material, attached to the distal portion of an imaging catheter. The imaging catheter is inserted into the patient and the transducer is positioned within the patient to image a desired region of the patient's anatomy.
Such catheters typically operate by sending an electrical signal or excitation pulse to the transducer. The transducer converts the electrical energy into mechanical energy, which propagates into a patient's surrounding body tissues as an ultrasonic wave. The frequency of the emitted ultrasonic waves are a function of the resonant frequency of the transducer element and the frequency content of the excitation pulse. The ultrasonic waves are reflected back to the transducer as reflected signals or echoes, which the transducer converts into an electrical signal. This electrical signal is used to produce an image of the patient's anatomy.
By operating with a single transducer, however, the images produced are limited to a single two-dimensional plane. As a result, the transducer must be moved within the patient to produce images over a larger area. Additionally, since the single transducer element has only one resonant frequency, the focusing capability of single transducer imaging catheters is limited. The frequency of emitted sound waves, which is a function of the resonant frequency and bandwidth of the transducer element and the frequency content of the excitation pulse, can only be varied by varying the excitation pulse frequency. As a result, the ability of a single transducer element to be focused at different depths into the surrounding tissue is limited.
It would be desirable, therefore, to provide an imaging catheter system capable of providing high quality ultrasound images. It is further desirable to provide for focusing in more than one plane to provide improved lateral resolution. It is also desirable to provide the capability to produce and receive multiple ultrasonic signals. It is further desirable to provide such a system for use with an ultrasonic imaging catheter.